U.S. patent number 4,034,206 [Application Number 05/685,331] was granted by the patent office on 1977-07-05 for range top element.
This patent grant is currently assigned to Gould Inc.. Invention is credited to Glen H. Penrod.
United States Patent |
4,034,206 |
Penrod |
July 5, 1977 |
Range top element
Abstract
A heating element assembly having a thermally conductive ceramic
top sheet against the underside of which is positioned a thermally
and electrically insulating base pod having a recess containing a
loosely secured, planar array of thin, flat strips of apertured,
foil-like, electrical resistance material. The array is spaced from
the ceramic sheet a predetermined distance and disposed in such a
manner as to provide a large amount of heat radiating surface
adjacent to the underside of the ceramic top. The spacing between
the array and the ceramic top sheet enhances even radiant heating
of the ceramic top. Such a heating element assembly is low in cost
and high in thermal efficiency, having particular utility as a
burner for a ceramic top electric range.
Inventors: |
Penrod; Glen H. (North Olmsted,
OH) |
Assignee: |
Gould Inc. (Rolling Meadows,
IL)
|
Family
ID: |
24751727 |
Appl.
No.: |
05/685,331 |
Filed: |
May 11, 1976 |
Current U.S.
Class: |
219/462.1;
219/541; 338/288; 219/542 |
Current CPC
Class: |
H05B
3/748 (20130101) |
Current International
Class: |
H05B
3/74 (20060101); H05B 3/68 (20060101); H05B
003/68 () |
Field of
Search: |
;219/460,463,464,465,466,467,468,541,542,546,552
;338/208,209,210,212,287,288,295,297,301,308,309 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Mayewsky; Volodymyr Y.
Attorney, Agent or Firm: Sachs; Edward E.
Claims
What is claimed is:
1. A heating element assembly comprising a thermally conducting
electrically insulating rigid ceramic sheet;
a block of thermally and electrically insulating material, a face
of said block having a wall projecting therefrom to define a recess
in said block, said block being positioned against said ceramic
sheet such that said recess and said sheet define a chamber;
and a planar heating element of apertured foil-like electrical
resistance material, said element being contained in said chamber
and being spaced from and in noncontiguous relationship with said
ceramic sheet, the periphery of said element defining a plane
parallel to said ceramic sheet, said wall containing a plurality of
cavities, said cavities each containing a peripheral portion of
said element, said planar heating element of apertured foil-like
electrical resistance material being in the form of an array of
thin flat strips, said strips being equidistantly spaced from each
other and electrically connected to each other.
2. A heating element assembly according to claim 1, wherein said
material is an expanded metal foil grid.
3. A heating element assembly according to claim 1, wherein said
element is integrally formed by powder rolling.
4. A heating element assembly according to claim 1, wherein said
element is integrally formed by photographic etching.
5. A heating element assembly according to claim 1, wherein said
strips are electrically connected in end-to-end series
relation.
6. A heating element assembly according to claim 1, wherein said
strips are straight and parallel to each other.
7. A heating element assembly according to claim 1, wherein said
strips are circular, said strips being arranged to form a series of
concentric circles.
8. A heating element according to claim 1, wherein said wall
defining said recess has at least one aperture, said aperture being
useful for electrically connecting said array to an electrical
power source external to said chamber.
9. A heating element assembly according to claim 8, wherein said
chamber is generally cylindrical.
10. A heating element assembly comprising a thermally conducting
electrically insulating rigid ceramic sheet;
a block of thermally and electrically insulating material, a face
of said block having a wall projecting therefrom to define a recess
in said block, said block being positioned against said ceramic
sheet such that said recess and said sheet define a chamber;
and a planar heating element of apertured foil-like electrical
resistance material, said element being contained in said chamber
and being spaced from and in noncontiguous relationship with said
ceramic sheet, said element defining a plane parallel to said
ceramic sheet, said heating element of apertured foil-like
electrical resistance material being in the form of an array of
thin flat strips of constant width, said strips being equidistantly
spaced from each other and electrically connected in end to end
series relation, said wall containing a plurality of cavities, said
cavities each containing a peripheral portion of said array.
Description
BACKGROUND OF THE INVENTION
The present invention is in the field of heating element assemblies
for electric ranges.
More particularly, the present invention relates to a heating
element assembly for a smooth surface ceramic top electric range.
Prior art heating assemblies for such ranges included an insulating
pod with a recess therein and a helically coiled heating element
wrapped in a spiral manner within the recess. The element is
attached to the floor of the recess by a suitable adhesive.
Another prior art arrangement is shown in U.S. Pat. No. 3,749,883,
and includes an insulating pod having a recess therein which
receives a tubular electric heating element which is shaped to a
flat spiral. A metallic support member is formed of strip metal
positioned on edge and bent to provide a pair of legs connected by
a bite portion.
As is recognized by the patentees of that patent, difficulty has
been encountered in the design of an electric heater for use with a
ceramic panel because the composition of the latter becomes
unstable under excessive heat and discolors or fractures. Attempts
have been made to overcome this problem and have met with a certain
degree of success. The patentees also recognize that such attempts
have resulted in costly assemblies, and attention has been directed
by those patentees to utilization of a sheathed, tubular electric
heating element providing a flat, spiral heating surface. They also
recognize that the tubular electric heating element is relatively
expensive, but the low-cost assembly technique offsets the
increased cost of the heating element.
Improved heating element assemblies utilizing a nontubular,
foil-like, electrical resistance material are disclosed in the
copending application of Douglas H. Maake, Ser. No. 599,391, filed
July 28, 1975, and in U.S. Pat. No. 3,798,419 to Douglas H. Maake,
both assigned to the assignee of this application.
SUMMARY OF THE INVENTION
The present invention provides a heating assembly for a ceramic,
smooth top electric range having improved thermal efficiency,
faster heat-up and cool-down characteristics, and reduced power
consumption.
A thermally and electrically insulating base pod having a recess
containing a planar heating element array of thin, flat strips of
apertured, foil-like, electrical resistance material is positioned
against the underside of a thermally conductive ceramic top
sheet.
The heating element array is contiguous with the floor of the
recess and is spaced a predetermined distance from the ceramic top
sheet, the predetermined distance being directly related to the
depth of the recess in the base pod. The spacing between the array
and the ceramic sheet enhances even radiant heating of the ceramic
top sheet.
The planar heating element array contained within the recess is
comprised of a plurality of constant width flat strips of
apertured, foil-like electrical resistance material preferably in
the form of a grid. The strips have a length and width
substantially greater than their thickness. The strips are
electrically connected end to end in series relationship and are
geometrically arranged on the floor of the recess so that the
strips are equidistantly spaced from each other to form an array
having a generally circular periphery.
The areas defined by the lengths and widths of the strips are in a
plane that is adjacent and parallel to the ceramic top sheet. Such
an arrangement provides a large amount of heat radiating surface
equidistantly spaced from the underside of the ceramic top sheet,
thus enhancing even heating across the area of the ceramic sheet
exposed to the heating effect of the array. Such a heating element
assembly has excellent thermal characteristics, low assembly costs,
and improved efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of a heating assembly in accordance with the
present invention less the ceramic top sheet;
FIG. 2 is a not-to-scale cross sectional view along line 2--2 of
the assembly shown in FIG. 1 positioned against the underside of a
thermally conductive ceramic top sheet in accordance with the
present invention;
FIG. 3 is a perspective view of a section of the heating assembly
illustrated in FIGS. 1 and 2, with the ceramic top sheet removed
showing the access used to electrically connect the heating element
array to an external power source (not shown); and
FIG. 4 is a plan view of a heating element assembly with the
ceramic top sheet removed, illustrating an integrally formed
heating element array of concentric circular strips equidistantly
spaced from each other.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and more particularly to FIG. 1,
there is illustrated a block-like base pod 10 which is formed of a
suitable material, such as a kaolin clay-base ceramic fiber,
capable of withstanding relatively high temperatures, being both
thermally and electrically insulating. A face 12 of the block-like
base pod 10 contains a generally cylindrical recess 14 defined by a
circular wall 16 and a flat floor 18.
The floor 18 of the recess 14 supports a planar heating element
array 20. The array 20 is formed of a plurality of flat, constant
width strips 22 of apertured, foil-like, electrical resistance
material, the strips 22 each having a length and width
substantially greater than their thickness. The strips 22 are
geometrically arranged in a plane wherein they are equidistantly
spaced from each other.
The material used to form the strips 22 is a commercially available
material having suitable electrical resistance characteristics. As
shown in FIGS. 1, 2, and 3, the material forming the strips 22 has
a diamond-shaped, expanded metal configuration. The expansion of
the metal may be accomplished by first slitting a solid foil strip
intermittently so that the entire sheet has a series of closely
spaced, parallel cuts to permit expanding it laterally to form an
open series. Furthermore, the material may be formed by repeatedly
impacting and shearing diamond-shaped apertures in the foil, using
conventional machinery. The resulting material has a high surface
area-to-mass ratio and a faster heat-up and cool-down rate as
compared to a coiled heating element of the prior art.
The strips 22 are electrically connected end to end in series
relationship. The electrical interconnection of the strips 22 is
accomplished by electrically conductive clips 23 which are fastened
by mechanical crimping or spot welding to the appropriate ends of
the conductive strips 22. Alternatively, the interconnection of the
strips 22 could be accomplished by nonapertured, interconnecting
bridges integrally formed with the strips 22 and composed of
material identical to that of the strips 22.
Power tabs 24 extend laterally through the wall 16 and are used to
electrically connect the array 20 with an appropriate external
electrical power source (not shown).
The array 20 is loosely secured to the floor 18 of the recess 14 by
peripheral portions 25 of the array 20 which extend, as indicated
by the dashed lines illustrated in FIG. 1, into appropriate
cavities 38 (shown more clearly in FIGS. 2 and 3) in the lower
portion of the wall 16. Such an arrangement loosely secures the
array 20 within the recess 14 and especially limits the axial
movement of the array 20 while allowing for limited movement
necessary for thermal expansion and contraction of the strips 22.
Alternatively, the array 20 could be secured to the floor 18 by
means of staples.
FIG. 2 illustrates a cross sectional view along line 2--2 of the
heating element assembly illustrated in FIG. 1 positioned against
the underside of a ceramic top sheet 30. The base pod 10 may be
secured to the ceramic sheet 30 by biasing springs which bear
against the underside of the pod, or by other suitable supports.
The strips 22 interconnected by clips 23 rest on the floor 18 of
the recess 14 of the base pod 10. The array 20 is spaced from the
ceramic sheet 30 a predetermined distance approximately equal to
the depth of the recess 14. This arrangement permits even radiant
heating of the underside of the ceramic sheet 30.
When the recessed side of the base pod 10 is positioned against the
underside of the ceramic top sheet 30, a cylindrical chamber 35 is
formed which encapsulates the array.
FIG. 3 more clearly illustrates the extension of the power
connection tab 24 through an aperture 39 which is located in a
portion of the wall 16 adjacent to the floor 18 supporting the
interconnected heating element strips 22. The aperture 39, besides
providing access to chamber 35 for the electrical connection of the
array to an external power source, can also function to limit the
movement of the array, since portions of the array extend into the
aperture 39.
FIG. 4 illustrates another embodiment of the invention wherein a
base pod 40 has a face 42 containing a generally cylindrical recess
44. The recess 44 has a circular wall 46 and a flat, circular floor
48.
The floor 48 supports heating element array 50 which includes a
plurality of flat, constant width, circular strips 52 formed of
apertured, foil-like, electrical resistance material. The circular
strips 52 are discontinuous and geometrically arranged in a common
plane on the floor 48. The strips 52 are equidistantly spaced from
each other such that the strips 52 define a series of generally
concentric circles having their centers in common with the center
of said circular floor 48. The circular strips 52 are electrically
connected to each other in series relation by integrally formed
bridges 53. Electrical power is supplied via an integrally formed
inner power tab 54 and an integrally formed outer power tab 55. The
array 50, comprising strips 52, bridges 53 and power tabs 54,55,
can be integrally formed using manufacturing techniques well known
in the art, including mechanical punching, as earlier described.
Alternatively, the array 50 could be formed by powder rolling
wherein a flat face of a plate is coated with a suitable metallic
powder. The flat face contains the design of the array pattern
desired, including appropriate strip locations, interconnected
bridges, and power connection tabs. Excess powder is removed such
that only the etched areas contain metallic powder. Roller pressure
is applied to the remaining powder, which is then sintered by
appropriate means to form an array as illustrated in FIG. 4.
Alternatively, the powder in the etched area could be pressured and
sintered simultaneously. The array may also be formed by suitable
photoetching techniques, wherein, for example, a thin, foil-like
layer of suitable metal deposited on photographic film is
selectively etched in accordance with a suitable array pattern
photographically exposed on the film.
The inner power tab 54 is connected to a terminal 56 which extends
through the floor 18 to a point on the outer surface of the pod at
which an external power lead can be connected. Alternatively, a
suitable aperture could be provided in place of the terminal 56 to
allow access to the inner power tab 54 for connection to an
external electrical power source. The outer power tab 55 extends
through the wall 46 via an aperture schematically illustrated by
dotted lines 57. In operation, the face 42 of the base pod 40 is
positioned and held against the underside of a thermally conductive
ceramic top sheet in the manner heretofore described.
Although preferred embodiments of this invention are illustrated,
it is to be understood that various modifications may be resorted
to without departing from the scope of the invention disclosed and
claimed herein.
* * * * *